FIG. 1 shows a configuration diagram of a capacitance type pressure measurement apparatus by using a conventional diaphragm.
Referring to FIG. 1, the conventional technology has a sensor housing 12. The sensor housing 12 is formed with a first open tube 12-1 and a second open tube 12-2.
Referring to FIG. 1, the sensor housing 12 is formed with an electrode substrate 14, the electrode substrate 14 being attached with an electrode 14T. The electrode substrate 14 is formed with a through hole (not shown) to mutually communicate the first open tube 12-1 and the second open tube 12-2. Also, a diaphragm 16 is fixedly mounted between the electrode substrate 14 and the first open tube 12-1 to spatially isolate the electrode substrate 14 and the first open tube 12-1. An outer circumference surface of the diaphragm 16 is fixedly mounted on an inner side wall of the sensor housing 12. The diaphragm 16 is a conductor of an elastic material.
Referring to FIG. 1, the second open tube 12-2 is mounted with a getter pump 18 to make a space between the diaphragm 16 and the second open tube into a vacuum state. The getter pump 18 may actually be a gas remover, such as zirconium (Zr), thallium (Ti), etc., dropping pressure by adsorbing and removing gas through chemical reaction rather than a pump.
In the conventional technology, when the first open tube 12-1 is positioned in a measurement object region higher than vacuum pressure, the diaphragm 16 is convexedly bent toward the electrode 14T so that capacitance between the electrode 14T and the diaphragm 16 is changed. The conventional technology measures pressure in a measurement object region, in which the first open tube 12-1 is positioned, through the change in capacitance.
However, when the gas remover configuring the getter pump 18 is consumed, the conventional technology causes the inconvenience of replacing it.
Also, when the pressure in the measurement object region is normal pressure much higher than vacuum pressure being pressure at a place where the getter pump 12-2 is positioned, the conventional technology has a difficulty in measuring the pressure in the measurement object region due to a limitation associated with elastic deformation.